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From:   Arnd Bergmann <arnd@arndb.de>
Date:   Tue, 1 Oct 2019 17:41:19 +0200
Message-ID: <CAK8P3a3Js2dNhnRhP7PLadWZ69DZr1mz6DowN9HDJL4CFDAAFw@mail.gmail.com>
Subject: Re: [alsa-devel] [PATCH] ASoC: SOF: imx: fix reverse
 CONFIG_SND_SOC_SOF_OF dependency
To:     Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Cc:     Mark Brown <broonie@kernel.org>, Hulk Robot <hulkci@huawei.com>,
        YueHaibing <yuehaibing@huawei.com>,
        Daniel Baluta <daniel.baluta@nxp.com>,
        Liam Girdwood <lgirdwood@gmail.com>,
        Jaroslav Kysela <perex@perex.cz>,
        Takashi Iwai <tiwai@suse.com>, Shawn Guo <shawnguo@kernel.org>,
        Sascha Hauer <s.hauer@pengutronix.de>,
        Pengutronix Kernel Team <kernel@pengutronix.de>,
        Fabio Estevam <festevam@gmail.com>,
        NXP Linux Team <linux-imx@nxp.com>,
        ALSA Development Mailing List <alsa-devel@alsa-project.org>,
        Linux ARM <linux-arm-kernel@lists.infradead.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
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On Tue, Oct 1, 2019 at 5:32 PM Pierre-Louis Bossart
<pierre-louis.bossart@linux.intel.com> wrote:
> On 10/1/19 9:20 AM, Arnd Bergmann wrote:
> > CONFIG_SND_SOC_SOF_IMX depends on CONFIG_SND_SOC_SOF, but is in
> > turn referenced by the sof-of-dev driver. This creates a reverse
> > dependency that manifests in a link error when CONFIG_SND_SOC_SOF_OF
> > is built-in but CONFIG_SND_SOC_SOF_IMX=m:
> >
> > sound/soc/sof/sof-of-dev.o:(.data+0x118): undefined reference to `sof_imx8_ops'
> >
> > Make the latter a 'bool' symbol and change the Makefile so the imx8
> > driver is compiled the same way as the driver using it.
> >
> > A nicer way would be to reverse the layering and move all
> > the imx specific bits of sof-of-dev.c into the imx driver
> > itself, which can then call into the common code. Doing this
> > would need more testing and can be done if we add another
> > driver like the first one.
>
> Or use something like
>
> config SND_SOC_SOF_IMX8_SUPPORT
>         bool "SOF support for i.MX8"
>         depends on IMX_SCU
>         depends on IMX_DSP
>
> config SND_SOC_SOF_IMX8
>         tristate
>         <i.mx selects>
>
> config SND_SOC_SOF_OF
>         depends on OF
>         select SND_SOC_SOF_IMX8 if SND_SOC_SOF_IMX8_SUPPORT
>
> That way you propagate the module/built-in information. That's how we
> fixed those issues for the Intel parts.

Yes, I think that would work here as well, but it keeps even more
information about the specific drivers in the generic code. It also
requires adding more 'select' statements that tend to cause more
problems.

The same could be done with a Kconfig-only solution avoiding
'select' such as:

config SND_SOC_SOF_IMX8_SUPPORT
         bool "SOF support for i.MX8"
         depends on IMX_SCU
         depends on IMX_DSP

 config SND_SOC_SOF_IMX8
         def_tristate SND_SOC_SOF_OF
         depends on SND_SOC_SOF_IMX8_SUPPORT

      Arnd